HT1250 accessory

[IMBEJames]

I'm trying to interface a Telex EM200 to an HT1250 (thanks, Joe and Doug!)... I can't find schematics anywhere for the EM200, and the other thing I'm trying to figure out is how the accessory connector on the 1250 actually works... I have the service manual with the pinouts, but I still found myself scratching my head. I also cracked open a speaker mic, but that really didn't help all that much either.

Is there any info on this that someone knows of? I don't mind doing the reading, I just can't find it.

thanks all...
-Jamie

[Al]

Jim, option select 1, when it's pulled low(gnd) tells the uP in the HT1250 that an external accessory is attached. Option select 2 is ptt when pulled low(gnd) after the powerup self test has completed -OR- if the HT is programmed for VOX AND option select 2 is low before the radio completes its powerup self test then the HT uP goes into VOX mode on the channel selections that are programmed for VOX operation. You know the rest from looking at the pinouts.

[IMBEJames]

Ok now Im understanding this a little better. But something is still a little fuzzy.

OPTSEL 1 pulled low is Accessory.
OPTSEL 2 pulled low is PTT.

So if OPTSEL 2 (pin 5) is connected to GROUND (pin 7), the radio will transmit. But where is the mic connected in all this? I was counting, but ran out of pins!!! Pin 4 is EXT MIC, but only one side of it. Where does the other one go? Seems like all the pins are taken.

[Al]

Since the external mics are electret type they have to be biased properly in order to work. This is done with a positive voltage via the ext mic pin you mentioned. The (-) side of the electret is connected to the ground pin on the radio's accessory connector.

[IMBEJames]

...now to figure out the pinout of the EM200 hirose connector. Or find a schematic...

There definitely isn't much literature out there for these things. If anyone has any ideas, I'm all ears.

thanks
-jamie

[ahab]

I have several of these units and have interfaced them with sabers. They are typically internally marked for the specific radio they are intended for and have VERY different internal circuit boards for different radios. So hopefully you can get your unit to work. the pinout I have is

EM200 Pinout
Spkr+ Pin1
Mic+ Pin2
OptSel Pin3
Grnd Pin4

This is a 6 pin connector, so its from the top going counter clockwise if I remember right.

If you could let me know what the HT-1250s accy pinout is I would appreciate it.

[IMBEJames]

Ahab, do you know where they are marked (and how)? I got one unit working after a few minutes on the phone with Telex yesterday. The other one will key the radio, I get Rx audio without any problems, but no mic audio. Not being too familiar with the Sabers, Im wondering if i have one for a saber that just wont work. It could also be a problem with any of the components, there was still a battery inside that had exploded. Lots of corrosion and a couple bad traces.

Here's what I have... looking at the Hirose from the outside of the box, pin 1 is at the top under the large alignment tab, then go clockwise. This is all just straight cabling, no other components needed. Makes me wonder how Telex can get $239 for a cable

pin 1 EXT SPEAKER +
pin 2 EXT MIC
pin 3 OPT SEL 2
pin 4 OPT SEL 1 and GROUND

On the HT1250, the pinout is

pin 1 EXT SPEAKER +
pin 2 EXT SPEAKER -
pin 4 EXT MIC
pin 5 OPT SEL 2
pin 6 OPT SEL 1
pin 7 GROUND

Pins 6 and 7 are shorted inside the 1250 accy connector, and EXT SPEAKER - is not used.

Also, do you know what model hirose connector that is? I think its an SR30 series, but im not exactly sure.

As for the second unit, I dont think Im going to dump much money into repairing it. Im half-tempted to try a Peltor ear bone mic, as I already have one of their PTT interfaces.